In recent years, the introduction of smart meters which are next-generation watt-hour meters that measure electric power digitally and are provided with a communication function within the meter, has continued to be promoted with the object of stability, efficiency, and so on, of electric power supply and demand. There is a need for a current sensor that achieves the broad dynamic range and high resolution that are required in a smart meter, with low power consumption.
In order to achieve a high resolution current sensor, it is effective to employ a magnetoresistance element having high sensitivity to a magnetic field. Moreover, in order to obtain both high resolution and broad dynamic range, a magnetic balance system current sensor employing a magnetoresistance element has been proposed. However, in the magnetic balance system, when a current-to-be-measured becomes large, it is necessary to generate in a coil a cancelling magnetic field having the same magnitude as a large current-induced magnetic field generated by the current-to-be-measured. In this case, a current passed through the coil to generate the cancelling magnetic field increases proportionately to a magnitude of the current-to-be-measured, hence there is a problem that in the case of a large current-to-be-measured, power consumption of the current sensor itself ends up increasing.
The current sensor, current measuring module, and smart meter according to the present embodiments provide a current sensor, current measuring module, and smart meter that enable high-precision measurement over a wide measurement range with low power consumption.